Preliminary study of a leak microstructure detector as a new single-electron counter for STARTRACK experiment

At Legnaro INFN Laboratories a track nanodosimetry experiment (STARTRACK) is installed in order to investigate the ion energy release in nanometric biological target. The nanodosimeter consists of a wall-less sensitive volume (SV), a series of collection electrodes and a single-electron detector, i.e. a drift column and a multi-step avalanche chamber (MSAC). To resolve temporally all the electrons collected from the SV, the possible replacement of the MSAC with a position sensitive gas counter has been investigated. In order to test if the leak microstructure (LM) counter can be used to detect single-electron in STARTRACK nanodosimeter, single-electron pulse-height spectra were measured in propane gas at low pressure (3 mbar). Experimental data show good prospects for this single step detector: LM detects single-electrons operating in proportional mode also at low pressure, the pulse-height spectra are well fitted by the theoretical Polya distribution, allowing to calculate the single-electron multiplication efficiency, which can reach a value of about 96%, quite similar to that of the MSAC detector.